Review question
We reviewed the evidence about the effect of mechanical ventilation at night in people with chronic (i.e. persistent) difficulties with breathing spontaneously due to diseases of the nerves, muscles or chest wall.
Background
Weakness of muscles of breathing or changes in the control of breathing are major complications of diseases of the nerves or muscles and of the chest wall. These problems can lead to hypoventilation, which is a state in which not enough air enters the lungs. People may then need devices to help them breathe (mechanical ventilation). Mechanical ventilation is widely offered to people with nerve and muscle diseases or chest wall deformities who develop chronic hypoventilation. We wanted to discover whether mechanical ventilation at night improved survival and symptoms of hypoventilation in this group and to compare different types of ventilation.
Study characteristics
This review includes 10 clinical trials involving 173 participants with persistent, stable hypoventilation. Three trials included only participants with motor neuron diseases, in three all participants had chest wall deformation only, and one trial included only participants with Duchenne muscular dystrophy. The other three trials had mixed populations.
The trials were comparisons of mechanical ventilation and standard care (five trials), different methods of ventilation (four trials) or both (one trial).
Key results and quality of the evidence
We found that mechanical ventilation at night may relieve the symptoms of chronic hypoventilation and prolong survival. However, the quality of the studies was very low. The benefit of long-term mechanical ventilation should be confirmed in further trials.
The evidence is current to June 2014.
Current evidence about the therapeutic benefit of mechanical ventilation is of very low quality, but is consistent, suggesting alleviation of the symptoms of chronic hypoventilation in the short term. In four small studies, survival was prolonged and unplanned hospitalisation was reduced, mainly in participants with motor neuron diseases. With the exception of motor neuron disease and Duchenne muscular dystrophy, for which the natural history supports the survival benefit of mechanical ventilation against no ventilation, further larger randomised trials should assess the long-term benefit of different types and modes of nocturnal mechanical ventilation on quality of life, morbidity and mortality, and its cost-benefit ratio in neuromuscular and chest wall diseases.
Chronic alveolar hypoventilation is a common complication of many neuromuscular and chest wall disorders. Long-term nocturnal mechanical ventilation is commonly used to treat it. This is a 2014 update of a review first published in 2000 and previously updated in 2007.
To examine the effects on mortality of nocturnal mechanical ventilation in people with neuromuscular or chest wall disorders. Subsidiary endpoints were to examine the effects of respiratory assistance on improvement of chronic hypoventilation, sleep quality, hospital admissions and quality of life.
We searched the Cochrane Neuromuscular Disease Group Specialized Register, CENTRAL, MEDLINE and EMBASE on 10 June 2014. We contacted authors of identified trials and other experts in the field.
We searched for quasi-randomised or randomised controlled trials of participants of all ages with neuromuscular or chest wall disorder-related stable chronic hypoventilation of all degrees of severity, receiving any type and any mode of long-term nocturnal mechanical ventilation. The primary outcome measure was one-year mortality and secondary outcomes were unplanned hospital admission, short-term and long-term reversal of hypoventilation-related clinical symptoms and daytime hypercapnia, improvement of lung function and sleep breathing disorders.
We used standard Cochrane methodology to select studies, extract data and assess the risk of bias in included studies.
The 10 eligible trials included a total of 173 participants. Roughly half of the trials were at low risk of selection, attrition or reporting bias, and almost all were at high risk of performance and detection bias. Four trials reported mortality data in the long term. The pooled risk ratio (RR) of dying was 0.62 (95% confidence interval (CI) 0.42 to 0.91, P value = 0.01) in favour of nocturnal mechanical ventilation compared to spontaneous breathing. There was considerable and significant heterogeneity between the trials, possibly related to differences between the study populations. Information on unplanned hospitalisation was available from two studies. The corresponding pooled RR was 0.25 (95% CI 0.08 to 0.82, P value = 0.02) in favour of nocturnal mechanical ventilation. For most of the outcome measures there was no significant long-term difference between nocturnal mechanical ventilation and no ventilation. Most of the secondary outcomes were not assessed in the eligible trials. Three out of the 10 trials, accounting for 39 participants, two with a cross-over design and one with two parallel groups, compared volume- and pressure-cycled non-invasive mechanical ventilation in the short term. From the only trial (16 participants) on parallel groups, there was no difference in mortality (one death in each arm) between volume- and pressure-cycled mechanical ventilation. Data from the two cross-over trials suggested that compared with pressure-cycled ventilation, volume-cycled ventilation was associated with less sleep time spent with an arterial oxygen saturation below 90% (mean difference (MD) 6.83 minutes, 95% CI 4.68 to 8.98, P value = 0.00001) and a lower apnoea-hypopnoea (per sleep hour) index (MD -0.65, 95% CI -0.84 to -0.46, P value = 0.00001). We found no study that compared invasive and non-invasive mechanical ventilation or intermittent positive pressure versus negative pressure ventilation.